Alignment telescope



Oct. 27, 1959V c. w. KEUFFEL ETAL 2,909,964

AIGNn/:ENT TELESCOPE original Filed June 2o, 1952 3 Sheets-Sheet l CARLW. KEUFFEL CONWAY D. HILLMAN ALLISTER L. BAK R o9 m m E N om m o m H vNv W W III 1 l FIM I ,.1 l :.l NQ SE mi om mm v2 f w! w\ o o NQ Si m1 o2@E ATTO EY Oct. 27, 1959 c. w. KEUFFEL ETAL 2,909,964

ALIGNMENT TELESCOPE 5 Sheets-Sheet 2 Original Filed June 20, 1952 M NR a2 SLAW.b Y 3 .mFLB Nwl WEH-L m NKDR. M 3 l A E WMT LW RNL AOL CCA Oct.27, 1959 c. w. KEuFFl-:L ETAL 2,909,964

v ALIGNMENT TELEscoPE 3 Sheets-Sheet 3 Original Filed June 20, 1952JNVENTOR. CARL w. KEUFFEL By coNwAY o. Hu. LMAN l'l L. BAKER l TORNEYUnited States Patent ALIGNMENT TELESCOPE Original application June 2i),1952, Serial No. 294,652,

now Patent No. 2,784,641, dated March 12, 1957. kDivided and thisapplication July 16, 1956, Serial No. 598,211

1 Claim. (Cl. 88-32) This invention relates to an optical instrument ofthe telescope class. More particularly it relates to a telescopesuitable for optical alignment work. Instruments of this general typehave recently been used quite extensively in the aircraft industry forlining up the component parts in the 'assembly of an aircraft. Some ofthese prior art instruments have micrometer means for measuring thevertical and horizontal displacements necessary to line up a particulartarget with the optical line of sight of the instrument. However inthese instruments, the micrometer means have been provided outside thetelescope objective which has made the instruments complicated in thestructure for operating the micrometer means.

The principal object of the present invention is to provide a telescopefor alignment work which includes optical micrometer means within thetelescope for measuring the displacement necessary to line up aparticular target with the optical line of sight of the instrument.

Another object of the present invention is to provide optical micrometermeans for a telescope, which means operates by translation of an opticalelement laterally transversely across the optical line of sight of thetele scope.

Another object of the invention is to provide optical micrometer meansfor a telescope which produces a displacement directly proportional tothe movement of the displacement means.

Another object of the present invention is to provide a telescope whichincludes optical micrometer means and which can focus from innity to apoint very close to the objective of the instrument.

These and other objects of the invention and the means for theirattainment will be more fully understood by reference to the followingdescription taken in connection with the accompanying drawing in which:

Fig. I is a view in plan of the new optical instrument.

Fig. II is a broken view in enlarged sectional plan taken Ithrough thecenter line of Fig. I.

Fig. III is a diagrammatic view showing an optical arrangement foranother embodiment of the invention.

Fig. 1V is a diagrammatic view showing an optical arrangement for athird embodiment of the invention.

Fig. V is a diagrammatic view showing an optical arrangement for afourth embodiment of the invention.

Fig. VI is a diagrammatic view showing an optical arrangement for a fthembodiment of the invention.

Fig, VII is a diagrammatic view showing an optical arrangement for asixth embodiment of the invention.

Fig. VIII is a diagrammatic view showing an optical arrangement for aseventh embodiment of the invention.

Fig. IX is a broken view in enlarged sectional plan of a completeembodiment of the instrument shown diagrammatically in Fig. VII.

Fig. X is a view in sectional elevation taken along the line X-X of Fig.IX and looking in the direction of the arrows.

Fig. Xl is a view in sectional elevation taken along v. je

fice

l 2 the line XI-XI in Fig. X and looking in the direction of the arrows.

The optical parts of tbe-first embodiment of the new telescope are shownin Fig. 11. They consist of a positivel objective lens 2, made up of apositive component 4 of crown glass and a negative component 6 of flintglass (the usual achromatic doublet combination); a negative lens 8,made up of a negative component 10 of crown glass and a positivecomponent 12 of flint glass (also an achromatic doublet combination); ashifting lens 14, preferably of high index glass, a positive lens 16,made up of a positive component 18 of crown glass and a negativecomponent 20 of flint glass (an achromatic cemented doubletcombination); the positive lens 16 is considered to be the secondobjective lens of the instrument since parallel rays entering the lrstobjective lens 2 will also enter the second objective lens 16 asparallel rays, a positive focusing lens 22, made up of a positivecomponent 24 of crown glass and a negative component 26 of liint glass(an achromatic cemented doublet combination); a reticle 28 which mayhave a curved surface to correct the position of the exit pupil and afour lens erecting eyepiece 30, the individual lenses of which are notshown in Fig. Il. The spacing between the objective 2 and the negativelens 8 is such that the second principal focus or" the objective 2 willcoincide with the first principal focus of the negative lens 8. Thusparallel rays entering the objective lens 2 will leave the negative lens8 as parallel rays. The second principal focus of a lens (whetherpositive or negative) is considered to be the point of convergence ordivergence after refraction of parallel rays coming from the directionof the object or target. Conversely, the trst principal focus of apositive or negative lens is the point of convergence or divergenceafter refraction of parallel rays coming from the opposite direction.

The shifting lens 14 is the equivalent of a Galilean telescope; i.e. itsradii of curvature R1 and R2 and its thickness t satisfy the formula:

where n is the index of refraction of the lens with respect to air. Theradii of all convex surfaces are considered positive and the radii ofall concave surfaces are considered negative. A glass of high index ofrefraction is preferably chosen for this component in order to keep thethickness low for the amount of displacement which must be accomplishedin shifting the lens. The transverse or lateral shifting of the element14 is understood to be a translational movement in the directionperpendicular to the optical line of sight of the instrument. 1f d isthe displacement caused by a transverse lateral shift S of the shiftinglens 14, then:

In terms of the thickness and refractive index:

d tOL-l) s- 'nRZ For a given displacement and any assumed R2, a higherindex of refraction, n, means that a thinner lens is required. When, asin Fig. II, the shifting lens 14 is internal, the equivalent of thedisplacement d at the target will be the quantity calculated from theabove formulae multiplied by the magnification of that part of theoptical system which comes in front of the lens 14, in this case thecombination of the objective lens 2 and Vthe negative Daseeeemr--fasashould be satisfied.

The shifting lens- 14 may be-used as shown with the convex surfacetoward the objective end of the telescope or it may be used with theconcave surface toward the objective end of the telescope. It ispreferred to place the convex surface toward the objective-end becausein this position the shifting lens -14 will tend to increase themagnication of the telescope whereas in the other position it will tendto decrease the magnification. However, in this embodiment, the effectof the shifting lens 14 on the magnification willusually'besmail.

The positive lens 16 tends to bring the light passing through theshifting lens 14 to focus on Vthe reticle 28. In the embodiment of Fig;II, the positive focussinglens 22 is required to actually bringthetlight to a focus. It would also be possible to -focus the 'positivelens 16 itself in which case the focussing lens 22 would not be requiredor a negative focussing lens could lbe used. However, a positivefocussing lens is preferred because it permits the instrument to befocussed down to a very close near distance. In fact with this type ofconstruction it is possible to design a system which canfocus right downto the front surface of the objective.

The four lens eyepiece within the tube 30 may be of the type commonlyused in surveying instruments or any other suitable eyepiece may beused. The overall magnification of the telescope, M, will be given bythe formula:

where m, equals which equals the magnification of the shifting lens, fpis the equivalent focal length of. the. combination of the positive lens16 and the focussing lens 22 and fe is the equivalent focal length ofthe eyepiece.

The objective 2 and the negative lens `8 are carried by the tube 40within the main tube 42. The objective 2 lits within the objective mount44, and is held therein by the threaded ring 46. The objective mount 44is threaded onto one end of the tube 40. This threaded connection mayalso be used for adjusting the spacing between the objective lens 2 `andthe negative lens 8. A mounting plate 48 is threaded onto the other endof the tube 40. The mount 50 for the negative component 10 of thenegative lens 8 is held against the mounting plate 48 by three screwsS2. `Oversize holes may be provided in the mount 50 for the screws 52 topermit centering of the negative lens 8 with the objective lens 2. Themount 54 for the positive component `12 of the negative lens 8 screwsover the mount 50 as shown. This threaded connection may also be usedfor the adjustment of the spacingr between the negative element 10 andthe positive element 12 "of the negative lens 8. A locking ring 56 isprovided to maintain this adjustment. Threaded rings 58 and 60"are` alsoprovided to hold the components 10 and 12 in their respective mounts Sand S4. A set screw 62 is provided to hold the tube 40 in the main tube42. A spherical surface which is centered with the optical axis may beprovided on the main tube 42 as is known in the art to form part of aball joint mounting for the telescope when in use.

The shifting lens 14 is carried in the transversely sliding mount 64 andheld therein with a threaded ring 66. The transversely sliding mount 64is heldebetween the enlarged outer end 68 of the tube 70 and the plate72. Three spacers 74 are provided between the'plate 7 2 and the enlargedend 68 of the tube 70 `and spacers 74 and plate 72 are heldthere-against by the screws 76. All of these parts are very accuratelymade to insure a close t and smooth sliding action. The transverselysliding mount 64 is moved by means of the sliding wedge 78 which slidesin a slot in the enlarged outer end of the tube 68 and a slot in theenlarged portion 80 of the tube 70. The action of the sliding wedge 78is counteracted by the leaf spring: 77 attached to the tube 70 by thescrews 79.

A rack S2 is secured to the sliding wedge 78. The rack 82 is engaged bythe pinion 84. The pinion 84 is held in the aide 86 by a set screw 88.The axle 86 ts in the bearing 90 which is provided with a flange that issecured to the casting 92 by the screws 94. The washer 96 is held ontothe axle 86 by the screw 98. The knob 100 is clamped to the washer 96 bymeans of the ring 102 and the screws 104. The nut 106 which is securedby a set screw 108 holds the aXle 86 in the bearing 90. A pin 110 passesthrough the casting 92 and the main tube 42 to prevent the casting 92from turning or sliding on the tube 42. The head of the pin 110 may actas a stop limiting the turning of the knob 100. A screw or screws 112may be provided inside the knob `100 to act against the pin 110 inlimiting the motion of the knob 100. The enlarged portions 68 and 80 ofthe tube 70 t accurately within the main tube 42 andthe tube 70 isprevented from sliding and turning in the tube 42 by the set screw 114.

The knob 100 is provided with a graduated drum 116 (Fig. I). e Thisgraduated drum 1-16 cooperates with an index mark on the outer edge ofthe flange of the bearing 90. The index mark is preferably providednearest the eyepiece end of the telescope for the convenience of theobserver. Since the displacement at the target is proportional to thetransverse movement of the shifting lens according to the formula givenabove, the scale on the graduated drum 116 is uniform. The angle 0 indegrees which the drum 100 must be turned in order to compensate adisplacement D at the target is given by therformula:

where p is the pitch diameter of the pinion 84 and a is the wedge angleof the sliding wedge 78. The graduation of the drum 116 is in accordwith this formula.

The same type of construction may be used for moving the shifting lensV14 in the verticalidirection and these means are operated by the knob118 (Fig. I) which is also provided with a graduated drum not shown forindicating the vertical displacement at the target.

The positive lens 16 is heldin the mount 120 by the tube 122 and thethreaded ring 124. The mount y120 fits in the tube 70 :and is heldtherein by a screw 79.

The positive focussing lens 22 is held inthe tube 126 by the threadedring 128.V The tube *126 fits inside the tube 70 and is free to slidetherein. A rack 130 is secured to the tube 126. The rack 130 alsoprevents turning of the tube 126 because it is limited by a slot in thetube 70. The rack 130 is operated by the pinion y132.which may be turnedby means of the knob '134 in exactly the same manner asrthe pinion 84 isturned by means of the knob 100.

The reticle 28 is spun or cemented in the mount 136 which is supportednear the eye end of the tube 70 by four adjustingsorews 138. Washers maybe provided between the heads of the adjusting screws 138 and the tube70. Pin holes are provided in the heads of the adjusting screws 138 topermit adjustmentof the reticle 136 in both the horizontal and verticaldirections. The cap 142 screws over the end ofthe tube 70 to cover theheads of the adjusting screws 138. The eyepiece bearing 144 screws intothe end of the tube 70. The eyepiece tube 30 carrying the four eyepiecelenses slides within the eyepiece bearing 144. A screw 146 is attachedto the side of the tube 30 and fits into a spiral slot in the eyepiecebearing V144. A sleeve 148 ts over the eyepiece bearing 144 to cover thespiral slot and is held in place by a screw 150. The knurled focussingring 152 is secured to the tube 30 by set screw 154. The ring 152 turnsthe tube 30 for focussing the eyepiece` on the reticle 28 by means ofthe spiral groove.

The optical system shown in Fig. III is essentially the same as theoptical system shown in Fig. l1 except that the negative lens 208 isshown as a single component in Fig. III and no special'focussing lens isprovided. The second principal focus of the objective lens 202.coincideswith the rst principal focus of the negative lens 208 so that parallelrays entering the objective lens 202 will leave the negative lens 208 asparallel rays. The shifting lens 214 may be moved transversely by themeans shown in Fig. II or any other suitable means. The positive lens216 brings the rays to a focus on the reticle 228 and the lens 216 maybe longitudinally adjustable for focussing the telescope on nearobjects. The eyepiece is made up of the four lenses 232, 234, 236 and238, parallel rays entering the objective 202 coming to a focus betweenthe third and fourth eyepiece lenses 236 and 238 and leaving the fourtheyepiece lens 238 as parallel rays.

In the embodiment of Fig. IV, the positive lens 308 is spaced from theobjective 302 so that its first principal focus coincides with thesecond principal focus of the objective 302. Parallel rays entering theobjective 302, leave the positive lens 308 as parallel rays. 'I'heshifting lens 314 lies between the positive lens 308 and the positivelens 316. The positive lens 316 focusses the rays on the reticle 328. Inthis case a two lens eyepiece made up of achromatic lenses 332 and 334is used giving an erect image because of the focal plane between theobjective lens 302 and the positive lens 308. The formulae given aboveapply to this embodiment, if m is taken as the magnification of thecombination of the objective lens 302 and the positive lens 308. It ispossible to make the optical system of Figs. II or III shorter than theoptical system of Fig. IV and Figs. II and III may be preferred for thisreason.

The shifting lens has utility other than in the type of telescopeillustrated in Fig. II. Fig. V shows a shifting lens 414 which is also aGalilean telescope used in front of the objective 402 of a simpleerecting telescope. The objective 402 forms an image of a target on thereticle 428 which is viewed through the four lens erecting eyepiece madeup of the lenses 432, 434, 436 and 438. In this embodiment, thedisplacement caused by the shifting lens is given directly by theformula:

In Fig. VI, the Galilean telescope shifting element 514 is made up of apositive lens 513 and a negative lens 515. The optical separation L ofthese two lenses is given by the formula:

f1 being the equivalent focal length of the lirst lens and f2 being theequivalent focal length of the second lens. The shifting lens in theother embodiments may also be considered a Galilean telescope, the firstsurface having an equivalent focal length,

R1 fl-n-l the second surface having an equivalent focal length,

R2 f n-l and the optical separation L being related to the thickness ofthe lens by the formula, L=t/n. In all other respects, the embodiment ofFig. VI is the same as the embodiment of Fig. III. However, the Galileantelescope made up of two components may be used in other embodiments ofthe invention in the same manner as the shifting lens and may also beused with either the positive 6 component or the negative componenttowardthe objective end of the telescope.

The transversely or laterally shifting part of the instrument may alsohave greater magnification than that which would be 4obtained from thetype indicated as elements 14, 214, 314, 414 and 514 in Figs. II-VI. Forexample, a telescope such as that made up by the positive lens 202 andthe negative lens 208 in Fig. III or such as the telescope made up bythe two positive lenses 302 and 308 in Fig. IV may be shifted laterallyaccording to this invention. The shifting lenses 214 and 314 would thenbecome unnecessary in Figs. III an-d IV and could be omitted.

The embodiment of Fig. VII is the same as the embodiment of Figs. IIIand VI except that a plano parallel tilting plate is used instead of atransversely shifting Galilean telescope. The plano parallel tiltingplate is known in the art but until now its use has been limited to aposition in front of the objective. The element 614 has dat planoparallel surfaces and operates by tilting about an axis whereas theGalilean telescopes 214 and 514.in Figs. III and VI operate by atransverse or lateral translational motion. The displacement caused by aplano parallel tilting plate is given by the formula:

It is evident that in this embodiment, the displacement is notproportional to the angle of tilt so a non-uniform scale must be used orsome other special means such as a cam provided to compensate thenon-proportional action.

The embodiment of Fig. VIII is the same as the embodiment of Fig. IIIexcept that illumination means are provided so that the telescope may beused as an autocollimator. For example, the illumination means may takethe formv of a lamp 740 and a partial reflector 742 (which may be merelya glass plate) for directing light through the reticle 728. Thus animage of the reticle 728 may be projected out through the objective 702to suitable reflecting means which direct the light back t0 theobjective 702 and through the rest of the optical system so that animage of the reticle is formed on the reticle. When the reticle is incoincidence with its image, the line of sight of the telescope isperpendicular to the reflecting means. In this manner, the instrumentmay be used for angular alignment as well as for transverse displacementalignment. The embodiments shown in the other figures may of course alsobe used for angular alignment if used in combination with a collimator.

in Figs. IX, X and XI, the parts numbered the same as 1n Fig. II aredescribed and function as has already been described in connection withFig. II.

The shifting lens 14 and all of the mechanism used to operate it whichis shown in Fig. II is omitted in Fig. IX. In Fig. IX a similar functionis obtained by means of the plano-parallel tilting plate 814, which ismounted 1n a metal ring 816, pivoted within the tube 42 by means of twop ivot pins 818, a pin 820 secured to the ring 816, extends into a slot822, in the rack 824, which is operated by means of the pinion gear 826,to move the pin 820, and thereby pivot the plano-parallel tilting plateabout the pins 818. The pinion gear 826, is turned by means of the knob828, secured thereto by a screw 830. The knob 828 is provided with ascale at 832 which in conjunction with an index mark provided on the rimof the bearing 834, which is attached to the tube 42, indicates thedisplacement of the line-of-sight caused by the tilting of theplano-parallel tilting plate 814. For example,

the scale 832 may be calibrated to read in thousandths of an inch.

Having thus described the invention, what is claimed A telescopecomprising an objective lens, a second lens within the telescope spacedfrom said objective lens at a distance so that its first principal focuswill coincide with the second principal focus of the objective lens, a.a third lens Within the telescope spaced further from said objectivelens than said second lens and receiving the 10 light from said secondlens a rcticle at a focal plane spaced further from said objective lensthan said third lens, an eyepiece focussed on said reticle, a planoparallel tilting plate between the second and third lenses, means fortilting said plano parallel plate to vary the displacement of the imageof a given target and means for measuring the tilt of said planoparallel tilting plate necessary to make said reticle appear inalignment with the given target.

References Cited in the file of this patent UNITED STATES PATENTS1,871,165 Egy Aug. 9, 1932 2,682,804 Cliiord et al. July 6, 19542,784,641 Keuffel et al Mar. 12, 1957

